1. Field
The present disclosure relates to a plasma display panel and related technologies including a method for forming the same. Implementations include a plasma display having a protective layer and a method for forming the plasma display and/or its protective layer.
2. Discussion of the Related Art
With the advent of a multimedia age, there is a rising demand for the appearance of a more delicate and larger display device capable of representing colors closer to natural colors. Since a current cathode ray tube (CRT) presently has limited application to large screen displays (e.g., 40 inches or more), a liquid crystal display (LCD), a plasma display panel (PDP), a projection television (TV), etc. are rapidly growing for expansion of use ranges thereof up to high-definition imaging fields.
The most outstanding characteristics of the above-mentioned display devices including the plasma display panel are that the display devices can be manufactured with a thinner thickness than the self-luminous CRT, achieve easy manufacture of a flat large-scale screen (for example, 60˜80 inches), and be clearly distinguished from the conventional CRT in a viewpoint of style or design.
The plasma display panel includes a lower panel having address electrodes, an upper panel having sustain electrode pairs, and discharge cells defined by barrier ribs. A phosphor is coated in each of the discharge cells, to display an image. More specifically, if a discharge occurs in a discharge space between the upper panel and the lower panel, ultraviolet rays generated by the discharge are incident to the phosphor to produce visible rays. With the visible rays, an image can be displayed.
Here, both the upper panel and lower panel of the plasma display panel are formed with dielectric layers, respectively, to protect the sustain electrode pairs and address electrodes. However, the upper dielectric layer formed on the upper panel may be worn and diminished due to a positive (+) ion shock caused upon a discharge of the plasma display panel. In this case, there is also a risk that a metal material, such as sodium (Na), etc. may cause a short of the electrodes. For this reason, magnesium oxide (MgO), having a high resistance against the positive (+) ion shock, has been conventionally coated over the upper dielectric layer formed on the upper panel.
However, the protective layer of the above-described plasma display panel has several problems as follows.
Firstly, when plasma in the plasma display panel is produced as a discharge gas upon receiving a voltage applied to the electrodes, ions contained in the plasma are introduced into the protective layer, thereby causing secondary electrons to be discharged from a surface of the protective layer. The discharge of secondary electrons consequently helps a gas discharge occur at a lower voltage. That is, the protective layer can efficiently endure the positive (+) ion shock, and has the effect of slightly lowering a firing voltage. As a result, the provision of the protective layer allows the panel to be driven at a low voltage. In turn, the low-voltage driving of the panel provides many advantages of reducing power consumption and consequently, production costs of the panel while achieving an improvement in brightness and discharge efficiency, etc.
However, MgO currently used as a material of the protective layer has a deficiency to efficiently lower a discharge voltage. This deficiency is due to material characteristics of MgO, and more particularly, is due to an extremely low discharge coefficient of secondary electrons in relation to ions introduced into the protective layer during production of plasma. More specifically, MgO has a strong covalent bond structure, and therefore, has a possibility of being easily bonded with foreign substances such as moisture, carbon monoxide, etc. Therefore, the protective layer may attain fine cracks at a surface thereof by a plasma particle shock, thereby suffering from a shortened lifespan and poor discharge efficiency of secondary electrons therefrom during an opposed discharge.
Secondly, when forming the protective layer using MgO, there is a problem of deterioration in jitter characteristics. As a result, the resulting plasma display panel has a deficiency of time to be assigned in a sustain period within one time frame during driving of the plasma display panel.
For example, when it is assumed that there exist 480 scan lines, and each line requires a scan time of 3 μs, and also, assumed that a single scan method for sequentially scanning from the first scan line to the last scan line is adopted, an address period, required in a single time frame divided into eight sub-fields, is more than 480×3 μs×8=13 ms.
Correspondingly, a time to be assigned in a sustain period within one time frame shall be shortened. A solution to assign a time more than such a deficient sustain period is to shorten a scan period. However, it is difficult to shorten the scan period because a scan pulse width must be lengthened in consideration of a jitter value during an address discharge. The jitter value is a discharge delay time caused upon an address discharge. The jitter value has some differences for each sub field, but belongs to a constant range during driving. Since the scan pulse includes such a jitter value, the scan pulse width inevitably becomes lengthened. As a result, the greater the jitter value, the longer the address period, and there exists a possibility of deterioration in picture quality.
A factor having the greatest effect on the jitter value during the address period is a discharge efficiency of secondary electrons from the protective layer. That is, the greater the discharge efficiency of secondary electrons from the protective layer, the smaller the jitter value. Since the scan pulse width is shortened as much as a reduced amount of the jitter value, consequently, the address period is shortened.